Thirty years ago on Wednesday, Mikhail S. Gorbachev became secretary general of the Communist Party of the Soviet Union. It was the start of a rocky tenure at the head of a system that ultimately proved impossible to sustain or to reform. Europe and the United States seized the moment, and steered the world through the largely peaceful fall of the Iron Curtain and the end of the Cold War. Shortly before the Berlin Wall fell, in 1989, Mr. Gorbachev advanced the vision of a “Common European Home,” in which a Europe “whole and free,” as the first President George Bush called it, would become a reality for all citizens of our Continent.

Much has happened since. We certainly missed an opportunity or two. There were disagreements across the Atlantic on policy issues, some of minor and some of major importance. But we stuck together, recognizing not just what our alliance had achieved — including the peaceful reunification of Germany, in 1990 — but also the value of facing future challenges united in a partnership based on a shared appreciation of personal freedom, the rule of law and the prosperity produced by open markets.

Today, the trans-Atlantic bond is being tested again. Crises are erupting ever closer to the European Union’s borders: the civil war in Syria, the upheaval in Libya, increasing refugee flows across the Mediterranean and, not least, the dangerous escalation brought about by Russia’s annexation of Crimea a year ago and the separatism in eastern Ukraine, stoked by Russian military support and supplies. The post-1989 European order is openly being called into question.

Germany and France have engaged in a determined diplomatic effort to tackle the crisis in Ukraine with the overriding objective of de-escalating the fighting and paving the way for a political resolution. This effort, based on a closely coordinated European and trans-Atlantic strategy, is founded on four pillars. First, we have taken a firm stance against Russia’s aggression through a calibrated series of measures, including sanctions. Second, we are strengthening NATO, along the lines agreed to at the Wales summit meeting in September. Third, we are supporting Ukraine’s transition through economic, humanitarian and political support. Finally, we want to engage Russia with the aim of ending the conflict and moving toward a more cooperative relationship.

Admittedly, trust is at a low point. The Minsk package, which the leaders of France, Germany, Russia and Ukraine agreed to last month, nonetheless provides an opportunity for calming an extremely fragile situation and outlines the path, however difficult, toward a politically negotiated solution. What is most urgently needed now is a substantially strengthened mission by the Organization for Security and Cooperation in Europe, which is overseeing the agreement, and redoubled efforts to help Kiev focus on the most pressing reform needs. We need shoes on the ground far more urgently than boots.

The challenges we face together extend far beyond Europe’s borders. The post-1945 international order — based on multilateral institutions and broadly accepted norms of state behavior — is under pressure from two distinct forces: the diffusion of power away from governments and the shift of power toward newly emerging countries. Embodied by the growing challenge of violent extremism on one hand and the tectonic shifts best exemplified by the remarkable rise of China on the other, these varied changes pose an unprecedented challenge to the world as we know it — and to our trans-Atlantic unity.

For Germany, the response to the dual challenges of crises and order will always be framed within a European approach. Germany will continue to invest in European integration because we profit from Europe’s strength. Only firmly anchored and integrated in Europe will we be able to shape the rules and norms of globalization — that includes the opportunity to conclude a mutually beneficial Transatlantic Trade and Investment Partnership that will set high standards and become a benchmark for similar trade agreements around the world.

Not just in recent crises, but also in pursuing the vision of a just, peaceful and resilient international order, Europe is America’s closest and most relevant partner. Germany will seek to play an efficient role as Europe’s “chief facilitating officer,” forging an ambitious and unified response to the challenges we are facing.

Germany does not shy away from making full use of its foreign policy tools. We are still very much present in stabilizing Afghanistan. We equip and train the Kurdish pesh merga forces against the threat of the Islamic State in Iraq. German military contingents also support the political stabilization effort in Mali and are the largest presence in Kosovo. Yet now more than ever, understanding the intended and unintended effects of our diplomatic and military instruments, as well as the limits of our capabilities, is an essential part of a viable foreign policy.

This does not mean embracing moral relativism. Yet holding firm to our moral precepts must go hand in hand with a realistic assessment of constraints and with strategic patience. This is as true for the United States, which has underwritten the current international order for many decades, as it is for Germany, which has profited immensely from this order and is starting to assume a broader international responsibility commensurate with its weight, its interests and its means.

In Washington this week, I am meeting with American officials to advance our dialogue about how best to address the present crises and to maintain a reliable, rules-based international order. While being aware and respectful of our different traditions and historical experiences, our countries must keep in mind the strategic virtue and value of trans-Atlantic unity in a changing and fragile world.